- Patients taking significant cytochrome P450 family 3, subfamily A, polypeptide 4 (CYP3A4) inhibitors or inducers, i.e. protease inhibitors (ritonavir, nelfinavir, etc), clarithromycin, ketoconazole, fluconazole, verapamil, diltiazem, carbamazepine, phenytoin, phenobarbital, Rifampin, efavirenz, nevirapine